For the purpose of improving reliability of data storage, a disk array apparatus is configured in such a manner that a plurality of magnetic or optical disk drives is mounted in a casing. The disk array apparatuses are connected with each other through dedicated high-speed network lines such as optical network lines, managed by management software, and utilized as SAN (Storage Area Network) disk array apparatuses, NAS (Network Attached Storage) disk array apparatuses, or a sole RAID (Redundant Array of Inexpensive Disks) disk array apparatus.
Each of the disk drives mounted on these disk array apparatuses is configured by a disk body mounting therein a disk, a driving motor, a head, an actuator, and the like, connectors for connecting electronic components for control, and the like. Main heating sources of the disk drive are the electronic components for control such as the driving motor, the actuator, and an LSI. The heat generated by these components is cooled by cooling air supplied by cooling fans provided in a disk array casing. If the disk array apparatus is poor in cooling capability, the temperature of the disk drives rises or the temperature varies between a plurality of disk drives. As a result, there is concern that the disk array apparatus malfunctions and reliability in the long term is deteriorated. For example, the variation in temperature between a plurality of disk drives causes deviation in timing of electronic circuits, which results in the possibility of a trouble in accessing from a controller to the disk drives and the possibility of a delay in time required to transfer data. Further, if the temperature of the disk drives rises, a lubricating layer applied on the surface of a magnetic disk is deteriorated and the magnetic disk is likely to be damaged.
Furthermore, it is an important issue to reduce noise generated by the cooling fans that are driven to supply cooling air to the disk drives in the disk array apparatus.
Moreover, in the disk array apparatus, reliability in data retention and data processing becomes extremely important. This fact is applied even in the event of a failure in a cooling system of the disk array apparatus itself. That is, even if a part of the fans for cooling the disk array apparatus fails to operate properly, the system needs to be operated without a halt until the repair is completed. In other words, it is necessary to secure cooling redundancy.
In accordance with a system configuration, a plurality of disk array apparatuses are horizontally installed or a sole disk array apparatus is vertically installed on, for example, a standard 19-inch rack in many cases. Accordingly, it is important that the cooling capability including the cooling redundancy is not affected by the installing direction of the casing.
As described above, the important issues for the disk array apparatus are as follows: a disk drive group needs to be cooled uniformly; the cooling redundancy for the disk drives needs to be secured; and noise generated by the cooling fans needs to be cut without being affected by the installing direction of the casing.
In a conventional disk array apparatus, there is shown a technique for preventing the cooling efficiency from rapidly decreasing by providing a shutter so that outside air does not flow back through the cooling fans in the event of a failure of the cooling fans (refer to Japanese Patent Laid-Open No. H11 (1999)-22698).
Further, in a conventional cooling apparatus for electronic devices, there is described a cooling technique in which a plurality of cooling fans are provided in the vicinities of heating components, and all the cooling fans are operated under the normal condition. If any one of the cooling fans fails to operate properly, air volume of the other cooling fans is controlled (refer to Japanese Patent Laid-Open No. 2005-57119).
Further, in a conventional disk array apparatus, there is disclosed a technique for improving a robust property and decay durability of a system by keeping some of a plurality of disk drives always in the standby mode (refer to Japanese Patent Laid-Open No. 2003-280823).
Further, in a disk storage apparatus, there is disclosed a control technique for stopping a write operation or spindle rotations when the temperature of an enclosure exceeds an allowable value due to a failure of the cooling fans (refer to Japanese Patent Laid-Open No. H05 (1993)-234237).
Further, in a conventional electronic device, there is disclosed a control technique in which combinations of a plurality of cooling fans arranged above and below a shelf, and the shelf, are divided into predetermined groups, and if the cooling fans fail to operate properly, an alarm is generated on a group unit basis and the group is made out of system (refer to Japanese Patent Laid-Open No. H03 (1991)-39880).
In the conventional technique according to Japanese Patent Laid-Open No. H11 (1999)-22698, the backflow can be completely prevented from occurring in the event of a failure of the cooling fans. However, since the shutter is opened and closed by its own weight, the installing direction of the casing is largely restricted. Further, there is a case wherein the sufficient amount of cooling air flow can not be obtained due to a large loss of air flow caused by keeping the shutter open. Further, there is a case wherein a slight difference in flow path condition produces a difference in flowing pressure between the plurality of fans, so that the shutter is intermittently opened and closed. In such a case, abnormal noise, which extremely annoys a user, is intermittently generated from the casing of the apparatus.
The conventional technique according to Japanese Patent Laid-Open No. 2005-57119 raises a problem of the air backflow through the cooling fans in the event of a failure of the cooling fans, which is also a problem in the conventional technique according to Japanese Patent Laid-Open No. H11 (1999)-22698. Therefore, it is necessary to prepare a plurality of large cooling fans having large fan properties in order to secure the sufficient amount of cooling air flow necessary and enough to cool all the disk drives in a good condition even in the event of a failure of the cooling fans. This case causes a problem of increasing noise generated by the fan.
The conventional technique according to Japanese Patent Laid-Open No. 2003-280823 allows the load of the disk drives to be equalized, and as a result, the temperature of the disk drives is equalized. However, the technique does not solve the problem that the temperature of the disk drives rises in the event of a failure of the cooling fans.
In the conventional technique according to Japanese Patent Laid-Open No. H05 (1993)-234237, although a control method by the disk drive alone is described, behavior of the whole system in which a plurality of disk drives is aligned is not disclosed.
In the conventional technique according to Japanese Patent Laid-Open No. H03 (1991)-39880, a combination of cooling fans arranged above and below a shelf and the shelf is classified as one group. In the case where a target electronic device is a disk array apparatus, the plurality of disk drives is accommodated in the shelf. In this case, if all the disk drives in the shelf are stopped due to a failure of the cooling fan, the usability of the system in the other disk drive group being operated is decreased, and in addition, the load of the system imposed by saving data for the disk drive group in the stopped shelf to the other disk drive group in the other shelf is increased. Alternatively, in many cases, it is difficult to place a plurality of cooling fans above and below each shelf due to a problem of securing spaces on the locations where the fans are placed and a problem of noise generated by the fans. In such a case, the cooling fans are arranged in front or rear of the shelf. However, in such a configuration, if the cooling fans in the shelf fail to operate properly, the disk drive group in the shelf needs to be stopped immediately and the cooling redundancy can not be secured.
The object of the present invention is to provide a disk array apparatus that enables to uniformly cool a disk drive group, to secure the cooling redundancy of a disk drive group, and to reduce noise generated by cooling fans without being affected by the installing direction of the casing.